Samples of plaque will be taken from carious and noncarious exposed root surfaces and the total viable count will be assayed on blood agar plates grown anaerobically after lightly ultrasonicating the specimen. Stimulated whole and paratod saliva samples will be taken over ice for a fixed time period and their microbiology assayed. The bacteria to be identified include: Streptococci, actinomyces, lactobacilli and veillonella. For Streptococci (S. mutans, milleri, mitior, and sanguis) samples will be cultured on TYC medium. The different morphological types will be counted. Colonies representative of each of the main morphological types will be gram stained and others picked off, grown in nutrient broth (Brain Heart infusion or Todd Hewitt) and identified in the API 20 streptococci identification strip. Not all streptococci will fall into the major known species and these will be noted. Counts of each of the identified species will be expressed as a percentage of the total viable count (TVC) detected on the blood agar plates. For actinomyces cultures will be grown on blood agar and representative colonies analyzed against specific anti-sera (kindly donated by Dr. G. Bowden) which will distinguish by agglutination between A. Israelii, A. Naeslundii (1 and 2), A. Viscosus and A. Odontolyticus. Lactobacilli, samples will be plated out on Rogosas medium. The total count on Rogosas medium can be expressed in relation to the total viable count on blood agar to give the percentage of lactobacilli. Speciation (C. casei, L. acidophilus and others) will be performed using a limited number of biochemical tests (details to be supplied by Dr. G. Bowden). Veillonella will be isolated on blood agar containing 7.5 micrograms per ml of Vancomycin. Representative colonies will be gram stained to identify those which are gram negative cocci, and the count expressed as for streptococci. Representative colonies will be picked off, grown up in nutrient broth and stored for more detailed analysis at a later date.